import java.util.ArrayList;
import java.util.Arrays;
import java.util.List;

public class Solution {
    public static List<List<Integer>> fourSum(int[] nums, int target) {
        List<List<Integer>>  list = new ArrayList<>();
        Arrays.sort(nums);
        for (int i = 0; i < nums.length; i++) {
            if (target > 0 && nums[i] > target) {
                return list;
            }
            if (i > 0 && nums[i] == nums[i-1]) {
                continue;
            }

            for (int j = i + 1; j < nums.length; j++) {
                if (j > i +1 && nums[j] == nums[j-1]) {
                    continue;
                }
                int left = j +1;
                int right = nums.length - 1;
                while (left < right) {
                    long sum = (long)nums[i] + nums[j] + nums[left] + nums[right];
                    if (sum > target) {
                        right--;
                    } else if (sum < target) {
                        left++;
                    } else {
                        list.add(Arrays.asList(nums[i],nums[j],nums[left],nums[right]));
                        while (left < right && nums[right] == nums[right-1]) {
                            right--;
                        }
                        while (left < right && nums[left] == nums[left+1]) {
                            left++;
                        }
                        right--;
                        left++;
                    }
                }
            }
        }
        return list;
    }

    public static void main(String[] args) {
        int[] nums = {1,0,-1,0,-2,2};
        System.out.println(fourSum(nums,0))
        ;
    }
}